I don't know if gearing would make any difference, I tried stomping on it from a 40/50 mph roll, and the engine went silent, BOG
I didn't read this whole thing, BUT something I don't think was mentioned is the secondary air flap has an adjustment on it that can be made tighter by turning a screw. MAY just take care of the problem. Just my nichels worth. Tom T.
Yep, he'll report his progress soon. For me, when you throw an aluminum intake on, the Holley goes on top automatically....
HAHAHA, yep thats exactly what the engine does with the Q-Jet on top of the SP3 when slammed to WOT. Other than that the engine runs fine with the Q-Jet on the SP3 I think, I dont really remember
3800 stall converter, will change everything. A good high efficiency converter, is not cheap, but will be with you for years of fun. I had stall converters in stockers that were fun to drive. They also can reach right over the BOG range that often occurs below 3000 rpm. Cheap converters slip at a higher percentage, waste power and fuel, overheat the fluid.
Gary, First time I have heard of this minor mod. What is the reason for this and can you provide a pic. Just learnin more Quad Mods. Thanks. Doug
The scratches, directly in front of the brass nozzles, help detatch the fuel from the slick surface. Same reason you never polish an intake manifold. Slight roughness keeps fuel suspended and flowing vs streaming along the surface. No big deal maybe but absolutely no downsides for a minute or two labor.
Those two little holes pointing at the front edge of the secondary air flap are designed to eject fuel just as the flap senses vacuun on full throttle. I enlarged them per Cliff Ruggles 2nd recipe and counter sunk them slightly to remove burrs. When i started the engine, I twisted the throttle open to see how it worked, I saw two streaks of fuel shoot right out. It was funny as hell to watch. The fuel is sucked out by vacuum, not pushed out like a Holley. This is his book. https://cliffshighperformance.com/product/how-to-rebuild-and-modify-rochester-quadrajet-carburetors
Is that fuel supplied by the secondary metering rods.......... Meaning do the rods have to start lifting before fuel is supplied, or are those holes on a separate circuit?
Those 2 tiny holes are fed by 2 "acceleration" well tubes that sit in fuel. When the back barrels are slammed open the air rushes in and the upper flap starts opening. As air rushes between the front edge of the flap and the choke air horn, the "vacuum" hits hard and fast pulling a shot of fuel into the secondary area. A split second the job is done, and the air valve is wide open and roaring.
I also cut two small notches in the front of the flap where the fuel holes are. (Ruggles book shows this) That allows a larger air rush to strengthen the fuel draw. That allowed me to use a fast, 1 second diaphragm, for rapid secondary opening. With high stall converters, this all works together.
One more thing. Set the air flap tension somewhere between 1/2 turn to 3/4 turn to and make sure there is no bog. Best setting has always been in that range for me. If not, buy a new spring and nylon flap lift cam while your at it.
